This invention relates to optical devices in general, and more particularly to optoelectronic devices.
Optoelectronic devices are electronic devices for emitting, modulating, transmitting and sensing light.
One important type of optoelectronic device is the vertical cavity surface emitting laser (VCSEL). VCSEL""s have recently generated considerable interest in the art. One reason for this interest is because VCSEL""s are believed to have application in a wide range of different optical telecommunication systems, e.g., wavelength division multiplexing (WDM) fiberoptic systems, switches, routers, etc.
A VCSEL generally comprises a substrate, a bottom mirror deposited on the top of the substrate, a bottom spacer deposited on the top of the bottom mirror, a gain region deposited on the top of the bottom spacer, a top spacer deposited on the top of the gain region, and a top mirror deposited on the top of the top spacer, such that a reflective cavity is formed between the bottom mirror and the top mirror, with the gain region being disposed within the reflective cavity. The gain region is constructed so that when the gain region is appropriately stimulated, e.g., by optical pumping, the gain region will emit light. The bottom mirror is typically substantially fully reflective at the wavelengths of interest, and the top mirror is typically partially reflective at the wavelengths of interest, so as to allow the laser light to build up within the reflective cavity before being emitted from the top end of the laser. It has been found that the laser light can become dissipated as it is reflected back and forth across the reflective cavity. Unfortunately, such dissipation reduces the efficiency of the laser. Thus, it would be advantageous if a lens could be provided within the reflective cavity so as to minimize light loss due to diffraction and to increase cavity stability.
Accordingly, an object of the present invention is to provide an improved VCSEL.
In one form of the invention, there is provided a VCSEL having improved diffraction loss, comprising a series of deposited material layers comprising the structure of the VCSEL, and an intracavity lens formed in one of the series of the deposited material layers.
In another form of the invention, there is provided a VCSEL which comprises a substrate, a bottom mirror deposited on the top of the substrate, a bottom spacer deposited on the top of the bottom mirror, a gain region deposited on the top of the bottom spacer, a top spacer deposited on the top of the gain region, and a top mirror deposited on the top of the top spacer, such that a reflective cavity is formed between the bottom mirror and the top mirror, with at least one of the bottom mirror, bottom spacer, gain region, top spacer and top mirror containing a superlattice structure, and with an adjacent region being subjected to ion implantation and rapid thermal annealing so as to disorder the superlattice structure and change its index of refraction, whereby to create an intracavity lens so as to reduce diffraction loss and to increase cavity stability.